Like many other things, learning theories have evolved with time.
Behaviorist theories have been part and parcel of learning for ever since we can remember. Then came cognitivist learning theories that highlighted the need to prepare the learner mentally so that he can cope with the learning and then given the techniques for effective storage and retrieval. Next came constructivist learning where learners need the "aha!" experience to discover new learning.
With the pervasiveness of the Internet comes "connectivist" learning. Argued by some to be a theory and others as not being one, it is how learning occurs among the millennials or the GenYs.
View the slides by Downes if you need to understand how this works.